The design and use of muzzleloading antique firearms (muzzleloaders) are well known. Muzzleloaders include (1) a barrel (with an open muzzle and a breach fitted with a plug) that holds the propellant charge and projectile at the breach end; (2) a primary ignition source, such as a percussion cap or flash pan filled with gun powder; (3) a striking device that ignites the primary ignition source either by impacting the percussion cap directly or by directing a spark into the flash pan; and (4) a small passage called a flash port, located at, or near, the breach end of the barrel, that directs the flash from the primary ignition source to the propellant charge. The function of the flash port is twofold, it directs the flash from the primary ignition source to the propellant charge and it prevents excessive back-flash from the burning propellant out of the rear of the barrel Increasing the cross sectional area of the flash port tends to enhance the desirable effectiveness of directing the flash from the primary ignition while tending to increase the undesirable back-flash. Thus the design of a flash port is necessarily a compromise. Excessive back-flash is undesirable both because it reduces the energy imparted to the projectile and because the ejecta poses a hazard to the user and persons near the rear of the muzzleloader. The function of the aforementioned striking device can be effected by passing an electric current through an ignition source or other schemes that might not involve, or appear to involve, a striking.
Herein, the term "percussion lock firearm" is used to encompass all guns using a primary ignition source that is separate from the propellant. Such a primary ignition source includes percussion caps, primers of all types, and flash pans. Also included are such ignition sources when using holders, spacers, disks, buffers or other auxiliary accessories.
Muzzleloaders that utilize a percussion cap as the primary ignition source are conventionally called cap-lock muzzleloaders or cap-locks. In cap-locks, the flash port is generally integrated into a removable nipple that also supports a percussion cap. Cap-locks are widely used by modern day hunters, and are the primary subject of the present invention. A threaded hole in the breach of the barrel of a cap-lock is fitted with a removable nipple that is configured to hold a percussion cap. The nipple supports the cap in a position that allows a hammer like striking device to impact the cap and thus initiate the primary flash.
Many configurations of percussion cap nipples have been introduced that conform to certain standard dimensions. Each of these designs strives to deliver the maximum primary flash into the barrel to ignite the propellant, while limiting back-flash.
The desirable goal of delivering a maximum flash to the propellant suggests a larger flash port would be better. However, a large flash port would allow excessive back-flash, outward through the flash port, of the high pressure gas generated by the burning propellant. Excessive back-flash is undesirable. It poses a hazard due to the presence of hot gasses and flying debris near the operator's face. Additionally, as a result of back-flash, smoke, soot and unburned propellant tend undesirably to accumulate on the mechanisms located near the gun's breach. Further, back-flash allows some of the propellent's pressure, which is intended to accelerate the projectile, to escape, thus undesirably lowering the muzzle velocity of the projectile.
Misfires (propellant fails to ignite) and hang-fires (propellant ignites after a significant delay) are common problems encountered in modern cap-lock muzzleloaders. An accumulation of unburned propellant (soot) in the path of the primary flash contributes to both misfires and hang-fires. In order to maintain the muzzleloader's accuracy, it is desirable to swab the barrel between shots. However, the act of swabbing the bore tends to move soot towards the breach end of the barrel and thus to deposit soot in the path of the primary flash, resulting in a hang-fire or a misfire on the subsequent shot.
Deactivation of the propellant is another cause of misfires and hang-fires in muzzleloaders. Oil used to clean the gun will deactivate the propellant on contact. Such oil fouling is common with in-line style cap-locks. The nipple is located in the center of the breach plug in in-ine cap-locks. During loading of the barrel with propellant and a bullet, the muzzle is pointed upward, which allows residual oil to flow downward and accumulate at the flash port. Thus, the greatest propellant deactivation occurs directly in the path of the primary flash.
FIG. 1 depicts a conventional percussion cap 30 and conventional nipple 20 installed in an in-line muzzleloader 10. Percussion cap 30 is seated on conventional nipple 20, which is within breach plug 14. When striker 16 strikes percussion cap 30, the explosive material within the cap is compressed between the cap's shell and the nipple's anvil 26 thus igniting the primary flash. The primary flash is directed into flash chamber 24 thence through flash port 22 and into barrel 12 past fouling 17, where it ignites propellent 18, which propels bullet 19. The high pressure gasses and flame from the burning propellant then travel back out through flash port 22 and flash chamber 24 lifting and sometimes fragmenting percussion cap 30. The present invention includes improvements to the prior art shown in FIG. 1.